Additional Gre Tunnel Parameters - Avaya G350 Administration

Configuring the router
Configuring GRE tunneling
The
tunnel keepalive
•
seconds
keepalive packets. The default value is 10.
•
retries
down. The default value is 3.
The following example configures Tunnel 1 to send keepalive packets every 20 seconds. If the tunnel's
destination interface fails to respond to three consecutive packets, the tunnel's source interface concludes
that the tunnel is down. The source interface continues to send keepalive packets, but until it receives a
response from the tunnel's destination interface, the tunnel informs hosts that send packets to the tunnel
that the tunnel is down.
G350-001# interface Tunnel 1
G350-001(if:Tunnel 1)# tunnel keepalive 20 3
Done!
NOTE:
You do not have to configure tunnel keepalive on both sides of the tunnel.
Dynamic MTU discovery
The size of packets that can travel through a GRE tunnel is limited by the lowest MTU of any router
along the route through the tunnel. When dynamic MTU discovery is enabled, the tunnel maintains an
MTU limit. At defined intervals, the tunnel's source interface sends a packet greater than this limit over
the tunnel to determine if the limit has changed, and updates the tunnel's MTU limit accordingly. When a
packet larger than the MTU arrives at the tunnel, if the packet is marked do not fragment, the tunnel's
source interface sends the packet back to the host requesting the host to fragment the packet. When
dynamic MTU discovery is disabled, the tunnel's source interface marks each packet as may be
fragmented, even if the packet's original setting is do not fragment. For more information on MTU and
fragmentation, refer to
Use the
tunnel path-mtu-discovery
dynamic MTU discovery by the tunnel. Use the
The
tunnel path-mtu-discovery
•
minutes
packet larger than the tunnel's current MTU limit through the tunnel to update the tunnel's
MTU limit.

Additional GRE tunnel parameters

Use the following commands to configure additional GRE tunnel parameters. For more information
about these commands, see Avaya G350 Media Gateway CLI Reference, 555-245-202.
•
Use the
checksum to the GRE header of packets traveling through the tunnel. When a checksum is
included, the tunnel's destination interface must perform checksum validation on incoming
packets. Packets without a valid checksum are discarded. Use the
disable checksums.
142
command includes the following parameters:
— the length, in seconds, of the interval at which the source interface sends
— the number of retries after which the source interface declares that the tunnel is
Overview of fragmentation
command in the context of the GRE tunnel interface to enable
command includes the following parameters:
— the length, in minutes, of the interval at which the source interface sends a
command in the context of the GRE tunnel interface to add a
tunnel checksum
on page 158.
form of this command to deactivate the feature.
no
no
Administration of the Avaya G350 Media Gateway
form of this command to
June 2004